Upgrade to Rails 6.0.0.

config/environments/development.rb

@@ -1,6 +1,4 @@
 Rails.application.configure do
-  # Verifies that versions and hashed value of the package contents in the project's package.json
-    config.webpacker.check_yarn_integrity = true
   # Settings specified here will take precedence over those in config/application.rb.
 
   # In the development environment your application's code is reloaded on
@@ -18,6 +16,7 @@ Rails.application.configure do
   # Run rails dev:cache to toggle caching.
   if Rails.root.join('tmp', 'caching-dev.txt').exist?
     config.action_controller.perform_caching = true
+    config.action_controller.enable_fragment_cache_logging = true
 
     config.cache_store = :memory_store
     config.public_file_server.headers = {
@@ -29,7 +28,7 @@ Rails.application.configure do
     config.cache_store = :null_store
   end
 
-  # Store uploaded files on the local file system (see config/storage.yml for options)
+  # Store uploaded files on the local file system (see config/storage.yml for options).
   config.active_storage.service = :local
 
   # Don't care if the mailer can't send.
@@ -54,7 +53,7 @@ Rails.application.configure do
   # Suppress logger output for asset requests.
   config.assets.quiet = true
 
-  # Raises error for missing translations
+  # Raises error for missing translations.
   # config.action_view.raise_on_missing_translations = true
 
   # Use an evented file watcher to asynchronously detect changes in source code,